In a known coating technique, an antireflective coating and a wavelength tunable film for interrupting specific wavelength light are applied over a wide area for solar cells, display panels, and lighting apparatuses.
A representative technique is, for example, a bar-coating method. An invention of the bar-coating method is described in Japanese Utility Model Laid-Open No. 62-183586. FIG. 6 is a schematic diagram for explaining the conventional bar-coating method.
As illustrated in FIG. 6, in the bar-coating method, a long bar 111 is first set in a coating width direction, and a coating liquid 114 is then supplied onto a substrate 113 from a separately provided dispenser nozzle 112. After that, the substrate 113 and the bar 111 in contact with the substrate 113 are relatively moved in a lateral direction to spread an excessive coating liquid in a scraping manner, leaving a predetermined volume of the coating liquid 114 on the substrate 113 so as to evenly form a thin film. Hereinafter, the dispenser nozzle 112 is located upstream while the coating liquid 114 scraped into a uniform film is located downstream with respect to the bar 111.
The surface of the bar 111 has small asperities. The coating liquid 114 is left on the substrate 113 such that the coating liquid 114 is as thick as gaps between the asperities and a substrate surface. Thus, a film thickness is adjusted by changing the size of the asperities.
As a bar used for the bar-coating method, a known bar shape is shown in, for example, Japanese Patent Laid-Open No. 2004-148204. FIGS. 7A and 7B are schematic diagrams illustrating the structure of a conventional bar. FIG. 7A is a side view of the bar. FIG. 7B is a cross-sectional view of the bar. A bar 111 illustrated in FIGS. 7A and 7B includes a wire 116 wound around a shaft 115, the wire 116 having a predetermined diameter. A coating liquid 114 is left on a substrate 113 according to a gap 117 formed between asperities on the wire 116 and the substrate 113, enabling coating with a constant thickness.